The strategy for implementing damage detection and the characterization of mechanical structures is commonly called Structural Health Monitoring (SHM). Damages are defined as modifications of the material and/or of the geometrical properties of a structural system, comprising modifications of boundary conditions and connections of the system, that worsen performance of the system. The SHM process implies the observation of the mechanical system along the time using periodically:                measurements of dynamic responses coming from an array of sensors,        extraction of data of damage characteristics sensed from these measurements, and        statistical analysis of these data of characteristics for determining the present health state of the system (also called structural analysis).        
The results (periodically updated) of this process provide information about the capacity of the structure for carrying out its function, considering the unavoidable aging and degradation in working environments. After extreme events, such as earthquakes or explosions, the SHM is used for a quick screening of the conditions of the structure for providing, almost in real time, reliable information about the integrity of the structure itself.
Nowadays, SHM systems use sensors placed on the surfaces to be controlled. For example, sensors used (anemometers for calculating the wind speed, accelerometers, extensometers, motion transducers, temperature sensors, sensors for detecting motion of weights, etc.) for monitoring bridges are placed on the external surfaces of beams, wire ropes or pillars, in order to:                estimate the effects of loads on the bridge,        evaluate the weakening of the bridge, and        foresee the probable evolution of the bridge and its expected lifetime.        
SHM systems have been devised with sensing devices including sensors (that for example may measure pressure, humidity, temperature, etc.) adapted to be buried in the structures to be monitored. These devices have at least one remote powering and transmission antenna for transmitting the measured values outside of the block of building material, as in RFID devices (that are sensorless) illustrated in the article by A. Finocchiaro, G. Ferla, G. Girlando, F. Carrara e G. Palmisano, “A 900-MHz RFID System with TAG-Antenna Magnetically-Coupled to the Die”, 2008 IEEE Radio Frequency Integrated Circuits Symposium, pages 281-284. This kind of sensing devices is disclosed, for example, in the U.S. patent applications No. 2004/0153270, 2012/0161789 and 2009/0033467 and in the PCT publication WO 2012/084295, herein incorporated by reference, and are depicted in FIGS. 1, 2, 3 and 4.
In order to supply the buried sensor even in structures of great size, it is known to use power supply shielded electric lines or devices, equipped with a receiving antenna and a transmitting antenna, that act as connections for transmitting in a contactless fashion, at a remote distance electromagnetic energy, required for powering the buried sensors. These shielded electric lines and the devices that act as contactless connections are buried in the cover portion (concrete cover or abutment stone) because the electromagnetic waves are strongly dampened even by relatively thin layers of concrete as well as by reinforcing bars buried in the building structure of reinforced concrete. Without them, it may not be possible to allow the remote powering antennas of the sensing devices buried in blocks of building material to receive an electromagnetic field of sufficient intensity for operating the sensing devices.
An inconvenience tied to the use of these buried devices is the limited reliability of the electric connections used for supplying them. In particular, in the building structures of great size, such as bridges, the electric or contactless power supply connections of the buried sensors may degrade along the time or may be damaged during catastrophic events.
As schematically shown in FIG. 5, that refers to the displacement of sensors and of contactless power supply connections disclosed in the PCT application WO 2012/084295 and the US Patent publication No. 2009/0033467 in the name of the same applicant, these contactless connections are typically buried in the cover portion. The cover portion is the portion of a building structure that more likely is damaged in case of fire or earthquake. Thus the electric connections and/or the contactless devices buried therein may be damaged just when, after a catastrophic event, it may be important to have them function correctly for powering the buried sensor and thus for having information about damage of the structure.